Iron silicon alloys



`Bune 7, 1966 w. A. GOERING ETAL 3,254,990

IRON SILICON ALLOYS Filed Nov. 6 1964 l Noam/O75' wcm/ EzAc/my w/LL /AM ,4. @OER/NG INVENTORS ATTORNEYS United States Patent O 3,254,990 IRON SILICON ALLOYS William A. Goering, Detroit, Mich., and Victor F. Zackay,

Berkeley, Calif., assignors to The Ford Motor Cornpany, Dearborn, Mich., a corporation of Delaware Filed Nov. 6, 1964, Ser. No. 409,505 2 Claims. (Cl. 75-123) This invention relates to alloys of iron and silicon, and more particularly to alloys of iron and silicon containing between four and six percent silicon and which have been found to be useful because of their unique magnetic properties. This invention is concerned with an iron silicon alloy of this type which has been modified to greatly enhance its ductility.

Iron silicon alloys of this nature are required in sheet form for the fabrication of electrical equipment such as motors, generators and transformers. The manufacture of this type of electrical equipment requires that the iron silicon sheet be cut or punched to the desired outline. These manufacturing operations require at least a modicum of ductility. The conventional iron silicon alloys of commerce have at best had only border line ductility.

The current invention is predicated upon our discovery that the ductility of these iron silicon alloys in the region of four to six percent silicon can be greatly enhanced by the addition of small amounts of hafnium or zirconium. As little as 0.05% of either of these metals added to a five percent iron silicon alloy has been found to markeclly increase the ductility of the product. Amounts of these elements up to 0.20% have been added and the increased ductility remains. The upper limit of the additions of these metals has not been established.

The sole figure of drawing is a graph in which the ordinate is 4the metal grain size and the abscissa is pery centage elongation in tensile tests. The dramatic effect of the addition of 0.10% zirconium to an alloy which is basically iron plus five percent silicon can be seen. The quenched alloys are of course more ductile than the annealed metal.

The vacuum melting techniques used to make the alloys are well known. The induction melting unit used was a special NRC chamber with a charging airlock, a rotating mold table, a retractable thermocouple tube and interior charging buckets. The top-pour crucible was made of high purity Zirconia and had a capacity of approximately 45 lbs. of molten iron.

The chamberwas pumped down to less than la pressure, and a-wash heat was made to clean and outgas the crucible. The crucible was then recharged with electrolytic iron through the airlock. The crucible did not hold the entire solid charge someltdown was accomplished in stages. A small carbon addition (.01-.03%) was charged initially to deoxidize the molten iron. The pressure usually rose to a during meltdown. Splashing due to the carbon-oxygen reaction was controlled by keeping a cover of unmelted iron above the molten liron until meltdown was complete. The cover also prevented splashing during subsequent charging. After the entire iron charge was melted, the silicon was added from previously loaded charging buckets within the furnace. The silicon used was Electromelt Purified Silicon, x 80 mesh. The addition was made with power off and although the reaction is exothermic, little superhe'ating occurred. The melt was then allowed to stand for several minutes at low power to mix the components, and other alloy additions were made at this time if scheduled. The temperature of the melt was then measured and adjusted to the predetermined pouring temperature, and the melt was poured into a ceramic launder which directed the stream into hot-topped, cast steel, chill molds. The ingots (and could not bev carried out at room temperature for most alloys. A test piece of each alloy was rolled prior to rolling of longer bars -to determine the lowest temperature at lwhich the alloy could be rolled without cracking. A list of the approximate rolling temperatures is included in the following table.

TABLE Warm working temperatures for. FeSi alloys Alloy Percent Addition Temp.,

Si C.

C89. 1. 02 -300 C85. 1. 73 300 C86 2. 87 300 4. 12 400 *Without 700 C. anneal.

The recrystallization temperature for these alloys is between 650 and 700 C. (1 hour), so it may be seen from the table that the alloys were not hot worked but warm worked at a temperature below the `recrystallization temperature. Bars that could not be rolled at a low warm working temperature on the first trial were annealed at 700 C. for l hour and then were usually nished Without cracking at the indicated temperature.

After fabrication the f/s bars were machined into standard ASTM tensile samples, annealed and pulled to failure lin a hydraulic tensile machine, at a head speed of approximately .05 in./minute. Threaded grips were used and the load elongation curves automatically recorded. Yield strengths were calculated from the curves at .02% offset. Ductility parameters (elongation and reduction in area) were measured on the broken samples. Data were obtained for samples slowly cooled or quenched from the recrystallization temperature.

A section of the threaded portion of the sample Was cut off and mounted so that a surface perpendicular to the tensile axis could be examined. The grain size was measured on this section using a lineal analysis technique. The sample was moved under the cross hairs on the microscope eyepiece and the grain boundary intersections counted along an arbitrary line. Then a similar traverse was taken at right angles to the first. The grain size was then calculated from the number of intersections K1 and Patented June 7, 1966 3 K2 and the lengths of the traverses L1 vand L2 by the equation .SKIKZ LiLz from which average grain diameters were calculated.

We claim as our invention:

1. A substantially carbon free ternary ferrous alloy consisting essentially from about 4% to about 6% silicon, from about 0.05% to about 0.20% of a metal selected from the group consisting of hafnium and zirconium and the remainder essentially all iron.

2. A substantially carbon free ternary ferrous alloy G.S. Grain size (gjmm) References Cited by the Examiner FOREIGN PATENTS 824,861 11/1937 France.

DAVID L. RECK, Primary Examiner.

P. WEINSTEIN, Assistant Examiner. 

1. A SUBSTANTIALLY CARBON FREE TERNARY FERROUS ALLOY CONSISTING ESSENTIALLY FROM ABOUT 4% TO ABOUT 6% SILICON, FROM ABOUT 0.05% TO ABOUT 0.20% OF A METAL SELECTED FROM THE GROUP CONSISTING OF HAFNIUM AND ZIRCONIUM AND THE REMAINDER ESSENTIALLY ALL IRON. 